Rubber composition comprising an epoxide elastomer cross-linked by a polycarboxylic acid

Abstract

A rubber composition is based on at least one predominant elastomer comprising epoxide functional groups, silica as predominant reinforcing filler, an agent for covering the silica, and a system for crosslinking the elastomer comprising an imidazole and a polycarboxylic acid of general formula (I): and an imidazole of general formula (II):

The invention claimed is: 
     
       1. A rubber composition based on:
 at least one elastomer comprising epoxide functional groups,
 wherein the predominant elastomer in the rubber composition is an elastomer comprising epoxide functional groups, 
 
 silica as predominant reinforcing filler, 
 an agent for covering the silica, and 
 a system for crosslinking the predominant elastomer comprising:
 a polycarboxylic acid of general formula (I): 
 
 
       
         
           
           
               
               
           
         
          in which A represents a covalent bond or a hydrocarbon group comprising at least one carbon atom, optionally substituted and optionally interrupted by one or more heteroatoms, and
 an imidazole of general formula (II): 
 
       
       
         
           
           
               
               
           
         
       
       in which:
 R 1  represents a hydrocarbon group or a hydrogen atom, 
 R 2  represents a hydrocarbon group, 
 R 3  and R 4  represent, independently of each other, a hydrogen atom or a hydrocarbon group, or else R 3  and R 4  form, together with the carbon atoms of the imidazole ring to which they are attached, a ring. 
 
     
     
       2. The rubber composition according to  claim 1 , wherein the at least one elastomer comprising epoxide functional groups represents from 30 to 100 phr as a blend with from 0 to 70 phr of one or more minor non-epoxidized elastomers. 
     
     
       3. The rubber composition according to  claim 2 , wherein the at least one elastomer comprising epoxide functional groups represents from 50 to 100 phr as a blend with from 0 to 50 phr of one or more minor non-epoxidized elastomers. 
     
     
       4. The rubber composition according to  claim 1 , wherein the at least one elastomer comprising epoxide functional groups represents all of the 100 phr of elastomer. 
     
     
       5. The rubber composition according to  claim 1 , wherein the at least one elastomer comprising epoxide functional groups exhibits a molar degree of epoxidation within a range extending from 0.1% to 80%. 
     
     
       6. The rubber composition according to  claim 5 , wherein the at least one elastomer comprising epoxide functional groups exhibits a molar degree of epoxidation within a range extending from 0.1% to 50%. 
     
     
       7. The rubber composition according to  claim 6 , wherein the at least one elastomer comprising epoxide functional groups exhibits a molar degree of epoxidation within a range extending from 0.3% to 50%. 
     
     
       8. The rubber composition according to  claim 1 , wherein the at least one elastomer comprising epoxidized functional groups is selected from the group consisting of epoxidized diene elastomers, epoxidized olefinic elastomers and mixtures thereof. 
     
     
       9. The rubber composition according to  claim 8 , wherein the at least one elastomer comprising epoxide functional groups is an epoxidized diene elastomer. 
     
     
       10. The rubber composition according to  claim 9 , wherein the at least one elastomer comprising epoxide functional groups is an epoxidized diene elastomer selected from the group consisting of epoxidized natural rubbers, epoxidized synthetic polyisoprenes, epoxidized polybutadienes, epoxidized butadiene-styrene copolymers and mixtures thereof. 
     
     
       11. The rubber composition according to  claim 8 , wherein the at least one elastomer comprising epoxide functional groups is an epoxidized olefinic elastomer. 
     
     
       12. The rubber composition according to  claim 11 , wherein the epoxidized olefinic elastomer comprises between 50 and 95% of olefin (molar percentages). 
     
     
       13. The rubber composition according to  claim 12 , wherein the epoxidized olefinic elastomer comprises between 65 and 85% of olefin (molar percentages). 
     
     
       14. The rubber composition according to  claim 11 , wherein the epoxidized olefinic elastomer is an epoxidized ethylenic elastomer. 
     
     
       15. The rubber composition according to  claim 1 , wherein A represents a covalent bond or a divalent hydrocarbon group comprising from 1 to 1800 carbon atoms. 
     
     
       16. The rubber composition according to  claim 15 , wherein A represents a covalent bond or a divalent hydrocarbon group comprising from 2 to 300 carbon atoms. 
     
     
       17. The rubber composition according to  claim 1 , wherein A represents a divalent hydrocarbon group comprising from 2 to 100 carbon atoms. 
     
     
       18. The rubber composition according to  claim 17 , wherein A represents a divalent hydrocarbon group comprising from 2 to 65 carbon atoms. 
     
     
       19. The rubber composition according to  claim 1 , wherein A is a divalent group of aliphatic or aromatic type or a group comprising at least one aliphatic part and one aromatic part. 
     
     
       20. The rubber composition according to  claim 1 , wherein A is a divalent group of aliphatic type or a group comprising at least one aliphatic part and one aromatic part. 
     
     
       21. The rubber composition according to  claim 1 , wherein A is a divalent group of saturated or unsaturated aliphatic type. 
     
     
       22. The rubber composition according to  claim 1 , wherein A is an alkylene group. 
     
     
       23. The rubber composition according to  claim 1 , wherein A is interrupted by at least one heteroatom selected from the group consisting of oxygen, nitrogen and sulfur. 
     
     
       24. The rubber composition according to  claim 23 , wherein A is interrupted by at least one oxygen atom. 
     
     
       25. The rubber composition according to  claim 1 , wherein A is substituted by at least one radical selected from the group consisting of alkyl, cycloalkylalkyl, aryl, aralkyl, hydroxyl, alkoxy, amino and carbonyl radicals. 
     
     
       26. The rubber composition according to  claim 1 , wherein A is substituted by one or more carboxylic acid functional groups and/or by one or more hydrocarbon radicals selected from the group consisting of alkyl, cycloalkyl, cycloalkylalkyl, aryl and aralkyl radicals, themselves substituted by one or more carboxylic acid functional groups. 
     
     
       27. The rubber composition according to  claim 1 , wherein A does not comprise another carboxylic acid functional group. 
     
     
       28. The rubber composition according to  claim 1 , wherein the content of polyacid is within a range extending from 0.2 to 100 phr. 
     
     
       29. The rubber composition according to  claim 28 , wherein the content of polyacid is within a range extending from 0.2 to 50 phr. 
     
     
       30. The rubber composition according to  claim 1 , wherein R 1  represents a hydrogen atom or an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group having from 5 to 24 carbon atoms, an aryl group having from 6 to 30 carbon atoms or an aralkyl group having from 7 to 25 carbon atoms, which group can optionally be interrupted by one or more heteroatoms and/or substituted,
 R 2  represents an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group having from 5 to 24 carbon atoms, an aryl group having from 6 to 30 carbon atoms or an aralkyl group having from 7 to 25 carbon atoms, which group can optionally be interrupted by one or more heteroatoms and/or substituted, 
 R 3  and R 4  independently represent identical or different groups selected from the group consisting of hydrogen, alkyl groups having from 1 to 20 carbon atoms, cycloalkyl groups having from 5 to 24 carbon atoms, aryl groups having from 6 to 30 carbon atoms and aralkyl groups having from 7 to 25 carbon atoms, which groups can optionally be interrupted by heteroatoms and/or substituted, or else R 3  and R 4  form, together with the carbon atoms of the imidazole ring to which they are attached, a ring selected from the group consisting of aromatic, heteroaromatic and aliphatic rings comprising from 5 to 12 carbon atoms. 
 
     
     
       31. The rubber composition according to  claim 30 , wherein R 3  and R 4  form, together with the carbon atoms of the imidazole ring to which they are attached, a ring selected from the group consisting of aromatic, heteroaromatic and aliphatic rings comprising from 5 to 6 carbon atoms. 
     
     
       32. The rubber composition according to  claim 1 , wherein R 1  represents a group selected from the group consisting of alkyl groups having from 2 to 12 carbon atoms and aralkyl groups having from 7 to 13 carbon atoms, which groups can optionally be substituted. 
     
     
       33. The rubber composition according to  claim 1 , wherein R 1  represents an optionally substituted aralkyl group having from 7 to 13 carbon atoms and R 2  represents an alkyl group having from 1 to 12 carbon atoms. 
     
     
       34. The rubber composition according to  claim 1 , wherein R 1  represents an optionally substituted aralkyl group having from 7 to 9 carbon atoms and R 2  represents an alkyl group having from 1 to 4 carbon atoms. 
     
     
       35. The rubber composition according to  claim 1 , wherein R 3  and R 4  independently represent identical or different groups selected from the group consisting of hydrogen, alkyl groups having from 1 to 12 carbon atoms, cycloalkyl groups having from 5 to 8 carbon atoms, aryl groups having from 6 to 24 carbon atoms and aralkyl groups having from 7 to 13 carbon atoms, which groups can optionally be substituted. 
     
     
       36. The rubber composition according to  claim 1 , wherein R 3  and R 4  form, with the carbon atoms of the imidazole ring to which they are attached, a phenyl, cyclohexene or cyclopentene ring. 
     
     
       37. The rubber composition according to  claim 1 , wherein the imidazole content is within a range extending from 0.01 to 4 molar equivalents with respect to the carboxylic acid functional groups present on the polycarboxylic acid of general formula (I). 
     
     
       38. The rubber composition according to  claim 37 , wherein the imidazole content is within a range extending from 0.01 to 3 molar equivalents with respect to the carboxylic acid functional groups present on the polycarboxylic acid of general formula (I). 
     
     
       39. The rubber composition according to  claim 1 , wherein the total content of reinforcing filler is within a range extending from 5 to 200 phr. 
     
     
       40. The rubber composition according to  claim 1 , wherein the silica content is within a range extending from 5 to 200 phr. 
     
     
       41. The rubber composition according to  claim 40 , wherein the silica content is within a range extending from 10 to 150 phr. 
     
     
       42. The rubber composition according to  claim 1 , wherein the reinforcing filler comprises carbon black in a minor amount. 
     
     
       43. The rubber composition according to  claim 42 , wherein the reinforcing filler comprises carbon black at a content within a range extending from 0.1 to 100 phr. 
     
     
       44. The rubber composition according to  claim 43 , wherein the reinforcing filler comprises carbon black at a content within a range extending from 0.1 to 30 phr. 
     
     
       45. The rubber composition according to  claim 1 , wherein silica represents the reinforcing filler in its entirety. 
     
     
       46. The rubber composition according to  claim 1 , wherein the agent for covering the silica is selected from the group consisting of hydroxylated or hydrolysable silanes, polyols, polyethers, amines, hydroxylated or hydrolysable polysiloxanes, guanidine derivatives, alkali metal or alkaline earth metal hydroxides, and mixtures thereof. 
     
     
       47. The rubber composition according to  claim 46 , wherein the agent for covering the silica is selected from the group consisting of amines, guanidine derivatives, alkali metal or alkaline earth metal hydroxides and mixtures thereof. 
     
     
       48. The rubber composition according to  claim 47 , wherein the agent for covering the silica is selected from the group consisting of primary amines, guanidine derivatives, alkali metal or alkaline earth metal hydroxides and mixtures thereof. 
     
     
       49. The rubber composition according to  claim 48 , wherein the agent for covering the silica is diphenylguanidine or octadecylamine. 
     
     
       50. The rubber composition according to  claim 49 , wherein the agent for covering the silica is present at a content within a range extending from 0.5 to 30 phr. 
     
     
       51. The rubber composition according to  claim 49 , wherein the agent for covering the silica is present at a content within a range extending from 1 to 15 phr. 
     
     
       52. A tire comprising the rubber composition according to  claim 1 . 
     
     
       53. The tire according to  claim 52 , wherein the agent for covering the silica is present at a content within a range extending from 0.5 to 30 phr and wherein the rubber composition serves as a tread composition.